Anencephaly: What’s the cause?
Finding answers to hard questions isn’t always possible
In 2012 a concerned nurse asked, “Are more babies in the Tri-Cities and Yakima area developing anencephaly?” She felt like there may be too many babies being born with this rare and fatal condition and asked us to find out if her hunch was right. Her question launched DOH into a four-year investigation of a condition that has long perplexed scientists and devastated families.
Anencephaly, a rare neural-tube birth defect, occurs when a baby’s brain and skull don’t fully form during the first month of pregnancy. Babies with anencephaly die before — or soon after — birth. Experts believe it is caused by a combination of genetic and non-genetic factors. Known risk factors for neural tube defects include low intake of folic acid, maternal diabetes, obesity, some medications, Hispanic ethnicity, and a previous neural tube defect-affected pregnancy.
Investigating clusters of rare conditions is notoriously difficult. And the outcomes can disappoint researchers, communities, and those personally affected by these tragic conditions, as it is not uncommon to find that no specific risk factor stands out. Even so, the Department of Health felt compelled to look further into the questions being raised, hoping to find a way to prevent this fatal birth defect.
The investigation
Our first investigative task was to find out if there really were more cases of anencephaly than would be statistically expected. A review of medical records found this was indeed happening. National estimates are that anencephaly affects between two and three pregnancies of every 10,000 in the US. What we found in the three-county area was 8.2 cases per 10,000 during 2010–2015 — but why?
To get to an answer, we dug into the research on what is known and what is not known about the causes of neural tube defects. We looked for common exposures or traits that many of the women in the study area might have shared: where the women lived, where they got their drinking water, what time of year the pregnancies began. Anything that could help explain the increase in this tragic birth defect.
We held community meetings, talked with healthcare providers, and listened to concerns including radiation, nitrates in drinking water, and pesticide exposure, among others. Some concerns were easily ruled out; others required connecting with national experts for their insights. One of the expressed worries was that past radiation releases on the Hanford site may be getting into the air, food, or water supplies.
Our agency is responsible for ensuring people in Washington are not unnecessarily exposed to radiation. In addition to our own monitoring for radiation in the air, water, soil and food, we provide oversight to other agencies to ensure their monitoring efforts are valid. As a result, our investigation had access to radiation health experts, decades of test results, and countless studies about health impacts of radiation exposure. We matched this evidence with what we knew about the places, food, and water supplies from the cases of anencephaly and found the likelihood of radiation exposure extremely low.
While we cannot say with 100 percent certainty that radiation or nitrates in drinking water did not play a role in any individual case, we do not believe these factors are responsible for the overall increased rate of anencephaly in the area. We used three approaches to assess potential for pesticide exposure and none of these indicated greater potential for exposure among parents of NTD-affected pregnancies compared to other pregnancies in the area.
Despite four years of study, we did not find a simple answer. While this is extremely disappointing, it is not unexpected; neural tube defects are complex conditions with intertwined risk factors. Much is still to be learned and as research sheds new light on anencephaly, we’ll align our future actions to prevent it.
The good news
While it’s disappointing that we didn’t find an explanation, the good news is that there is a simple way to prevent many neural tube birth defects — folic acid.
Our review of medical records early in the investigation indicated that both women with anencephaly-affected pregnancies and women with unaffected pregnancies in the area had low folic acid use prior to pregnancy. We looked at a survey of women across the state 2–6 months after delivery and found that women in the three-county area took folic acid less often in the month before pregnancy than women in the rest of the state. While we don’t know to what extent this contributes to the increased rates, we know the risk for neural tube defects is substantially reduced by getting the recommended amount of folic acid before and during pregnancy. So, we’re focusing much of our ongoing work on helping promote the use of prenatal vitamins among all women of reproductive age in the region
We worked with partners to get free prenatal vitamins for women in the area without healthcare coverage. We also supported an effort to get the USDA to add folic acid to corn masa. It is important that women take folic acid before they become pregnant. If a woman waits until she knows she’s pregnant, it could be too late to prevent neural tube defects.
The number of anencephaly cases in the Tri-Cities and Yakima area appears to be decreasing. We’re hopeful the combination of greater awareness and better access to folic acid will result in fewer pregnancies that develop this tragic birth defect. While we wait to see if the cases are indeed going down, we’re keeping our focus on promoting prenatal vitamins for all young women across Washington.
Visit our website for the final investigation report and more information on anencephaly.
Postscript
Our gratitude goes to the impacted families who gave their time and their insight to find answers that would help others.
We also wish to express our thanks to the many people and organizations for working so hard to help find answers and for their ongoing commitment to healthy babies and moms.
